Tech guide · Engine
Subaru Impreza timing belt guide
Every EJ-engined Impreza WRX and STI uses a rubber timing belt (cambelt), not a chain. The EJ20 and EJ25 turbo engines are interference engines: if the belt snaps or jumps a tooth, the pistons hit the valves, and the repair is usually a rebuilt or replacement engine. The belt is cheap; ignoring it is not.
At a glance
Interference engine
If the belt snaps, the valves hit the pistons. The repair is usually a new engine.
5 years or 50,000 miles
Our advice for older cars or unknown history: go by time as much as miles.
Do the water pump
It is driven by the belt. Change it, the tensioner and the idlers at the same time.
When to change it
| Situation | Recommendation |
|---|---|
| Subaru official interval (later US-market WRX and STI) | 105,000 miles or 105 months (2014–2016). 100,000 miles or 96 months on 2019–2021 STI. |
| UK specialist practice for older turbo Imprezas | Around 45,000–60,000 miles or 5–6 years, whichever comes first. |
| Just bought the car, with no dated invoice | Change it now. Japanese and UK imports very often have no proof it was done. |
| Car stood for a long time, or the belt is oil-soaked | Change it: age and oil degrade the belt regardless of mileage. |
Our advice for 20-plus-year-old cars with unknown history: go by time as much as mileage, and stick to around 5 years or 50,000 miles. Keep the invoice, with the date and mileage on it, for the next owner.
What should be replaced with it
- Timing belt: use a genuine or quality-brand kit (Aisin, Dayco and similar).
- Tensioner (hydraulic) and idler pulleys: a seized idler or a leaking tensioner will destroy a new belt.
- Water pump: it sits behind the belt. Doing it now saves paying the same labour twice.
- Thermostat and fresh coolant: good practice while the system is drained.
- Cam and crank seals if they are weeping oil: oil rots belts.
- Auxiliary (alternator and air-con) belts: they have to come off anyway.
Warning signs
- Whining or chirping from the front of the engine (often an idler or tensioner bearing)
- Oil or coolant around the timing covers
- No record of the belt ever being done
- Cracks, glazing or missing teeth if you can see the belt
DIY or garage?
It is a well-documented job, but it needs the correct cam alignment marks, the tensioner compressed and pinned, and the crank bolt torqued properly. If you are not confident, use a Subaru specialist: ask in the forum for recommendations near you.
More guides
Subaru Impreza service guide
Buying a used WRX or STI
Importing a Subaru to Ireland
Got a question? Ask the club
Subaru owners have been sharing know-how on the ISDC forum since 2000. Post your question and someone will have been there before.